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Radio Monitoring of the Sunand Space Weather

Thierry Dudok de WitUniversity of Orléans, France

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Optical Flare

Radio Burst

Fluctuating Total Electron Content

(TEC) Signal Fade, Change in Phase, Polarization, and Angle of Arrival

Difficulty Unloading “Dumping” Torque

Radar Range, Range Rate, and Direction Errors

Increased Neutral Density and Drag (LEO) Satellites

Spacecraft Commanding

Problems

Hazard to Exposed Humans in Space

Physical Damage to Spacecraft

Short Wave Fadeout

Depressed Maximum Usable

Frequencies (MUFs)

Communications Satellites Navstar Global Positioning System (GPS) Defense Support Program (DSP) Defense Meteorological Satellite Program (DMSP) and Other Low Earth Orbit (LEO) Satellites Geostationary Operational Environmental Satellite (GOES) and Other Geostationary Meteorological Satellites Tactical Warning and Attack Assessment (TW/AA) and Space Surveillance Network (SSN) Mechanical Tracking Radars TW/AA and SSN Phased Array Radars Passive Radio Frequency (RF) Tracking Receivers Ground-Based Electro-Optical Deep Space Surveillance (GEODSS) System and Other Optical Tracking Systems High Frequency (HF) Communications Systems HF Direction Finding Fixed and Relocatable OTH-B Radar Systems Low Frequency (LF) Long Range Navigation (Loran) and Very Low Frequency (VLF) Omega Navigation Systems Astronauts On Board the Space Shuttle and Passengers On Board High Altitude Aircraft (SST, U-2) Launch Vehicles Electric Power Transmission Lines, Petroleum Pipelines, and Telecommunications Cables Precision Instruments, Manufacturing Equipment, and Computers Magnetic Compasses, Navigation, and Survey Instruments (Homing Pigeons) Very High Frequency (VHF) Communications Systems Air Force Satellite Control Network (AFSCN) and Other Spacecraft Ground Tracking Stations Satellites that Depend Upon the Earth’s Magnetic Field for Reference in Spin Axis Alignment Spacecraft with Passive Radiators Designed to Operate at Temperatures Below 100 K Spacecraft that Depend Upon Star Patterns for Attitude Control

Anik DSCS FLTSATCOM AFSATCOM ALCOR (Kwajalein) ALTAIR (Kwajalein) Antigua Ascension Clear Haystack Haystack Auxiliary (HAX) Cobra Dane Eglin Fylingdales GEODSS - Socorro, Maui, and Diego Garcia Air Force Maui Optical Station (AMOS) Maui Optical Tracking and Identification Facility (MOTIF)

Intelsat Leasat Milstar UFO Kaena Point Millstone Hill MMW (Kwajalein) NAVSPASUR Pirinclik TRADEX (Kwajalein) PARCS Pave Paws Thule

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1, 2, 3, 4, 5, 13

4, 6, 7, 8, 9, 18

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Severely Degraded HF Propagation at

High Latitudes10

Radar Auroral Clutter, Noise, and

Interference (Auroral Paths)

6, 7, 8, 10,

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1, 2, 3, 4, 5, 6, 7, 8, 18

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10

4

6, 7

Polar Cap Absorption Event

Scintillation on Transionospheric

Paths

Internal Satellite Charging/Damage

to Internal Elec- tronic Components

Heat and Expand the Upper

Atmosphere

Range Errors on LF and VLF Navigation Systems

Deterioration of Spacecraft Surface Materials, Sensors and Solar Panels

Single Event Upset (SEU), Satellite Disorientation

Geomagnetically Induced Currents

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Location Errors on Navstar GPS

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14, 15

1, 2, 3, 4, 5, 12, 13, 21

1, 2, 3, 4, 5, 13

1, 2, 3, 4, 5, 13

Natural and Man-Made

Debris

Energetic Solar Flare Event

Sudden Ionospheric Disturbance

Medium Energy Particles

Geomagnetic Disturbance

Radio Frequency Interference (Solar

Radio Noise)

1, 2, 3, 4, 5, 6, 7, 8, 10,

17, 18

Spacecraft Surface Charging and

Discharge

1, 2, 3, 4, 5, 13

X-Ray Event

Fluctuating Geomagnetic

Field

15, 16, 19

Direct Thermal Input to Low

Temperature (IR) Systems

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Severely Degraded HF Propagation on

Transequatorial Paths

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Geostationary Magnetopause

Crossing (GMC)19

False Star Sensor Readings, Attitude Control Problems

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High Energy Solar Particles

(CME)

Coronal Mass Ejection (CME)

(Erupting Promi- nence or Disap-

pearing Filament)

Coronal Hole

Repeated Passage through Trapped Particle Radiation Belts

High Energy Galactic Particles

Exposure to Atoms (O) in the Thermosphere

Change in Solar Wind Velocity, Density, and/or

Direction

Equatorial Anomaly

Non-Great Circle HF Propagation

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Auroral Zone

Dashed line indicates theoretically possible, but unlikely, impact.

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Radio waves : the other side of the solar spectrumRadio waves : the other side of the solar spectrum

Radio waves ��

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Why are radio measurements of interest for spaceWhy are radio measurements of interest for spaceweather ?weather ?

•• Radio measurements presently provide the best remote access toRadio measurements presently provide the best remote access tofast earthbound CMEsfast earthbound CMEs

But the radio observation of CMEs is still a largely unexplored territory

•• CoronalCoronal magnetograms magnetograms can be made with radio measurements in can be made with radio measurements inthe GHz range (no other instrument can)the GHz range (no other instrument can)

•• Radio imaging, coordinated with other observations, should allowRadio imaging, coordinated with other observations, should allowthe complete evolution of flare-CME events to be trackedthe complete evolution of flare-CME events to be tracked

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OutlineOutline

•• The physics behind solar radio emissionsThe physics behind solar radio emissions

•• What are the different radio signatures of the Sun ?What are the different radio signatures of the Sun ?

•• What aspects of radio emission are relevant for space weather ?What aspects of radio emission are relevant for space weather ?➜➜ radio imagingradio imaging➜➜ radio burstsradio bursts➜➜ triangulationtriangulation➜➜ interplanetary scintillationinterplanetary scintillation

•• Existing and future facilitiesExisting and future facilities

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The physics of solar radioThe physics of solar radioemissionsemissions

just a brief introduction... just a brief introduction...

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How it startedHow it started

•• In 1942, J.S. Hey (GB), who was working on radars, noticed thatIn 1942, J.S. Hey (GB), who was working on radars, noticed thatinference occurred during solar flaresinference occurred during solar flares

•• In 1943, J.C. In 1943, J.C. Southworth Southworth (USA) started studying the Sun in the cm(USA) started studying the Sun in the cmfrequency rangefrequency range

•• After the war, a lot of veterans of the radar effort turned to radioAfter the war, a lot of veterans of the radar effort turned to radioastronomyastronomy

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Solar radio emission : some factsSolar radio emission : some facts

•• There are There are 3 distinct radio emission mechanisms3 distinct radio emission mechanisms in the solar in the solaratmosphereatmosphere➜➜ Thermal free-free bremsstrahlungThermal free-free bremsstrahlung➜➜ Gyromagnetic emissionGyromagnetic emission➜➜ Plasma emissionPlasma emission

•• The spectrum in the (10 MHz - 10 GHz) range is dominated by theThe spectrum in the (10 MHz - 10 GHz) range is dominated by theformer twoformer two

•• Spectral lines play no role and most of the polarisation is affectedSpectral lines play no role and most of the polarisation is affectedby Faraday rotationby Faraday rotation

•• The emission exhibits a rich dynamics near active regions andThe emission exhibits a rich dynamics near active regions andshocksshocks

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Radio waves : the characteristic figuresRadio waves : the characteristic figures

100 kHz 1 MHz 10 MHz 100 MHz 1 GHz 10 GHz

100 m 10 m 1 m 10 cm 1 cm1 km

Plasmawaves

Microwaves

Not accessible from ground100 GHz

1 mm

Thermal free-free bremsstrahlung :• caused by ion-electron collisions• mildly polarised• increases with ne, decreases with f2

Gyroresonance emission (synchrotron emission)• emitted by energetic electrons in strong magnetic fields• strongly polarised• intensity depends on which harmonics are absorbed

Plasma waves• coherent plasma waves are excited by energetic electron beams through nonlinear mechanisms• electromagnetic waves are emitted at the local plasma frequency, or harmonics thereof

� they’re the ones that are of interest for space weather

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A solar flare as seen atA solar flare as seen atvarious wavelengthsvarious wavelengths

Microwave emission (GHz) isstrongly correlated with hard X-ray emission, and to a lesserextent with EUV emission

� they all describe the samepopulation of energetic electrons

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Radio imagingRadio imagingat high frequenciesat high frequencies

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Nobeyama radioheliograph, T. Bastian

The Sun in cm wavelengths (17 GHz)The Sun in cm wavelengths (17 GHz)

Total intensity Circular polarisation only

post-flare loops : bremmsstrahlungand gyrosynchrotron emission from

100 keV electrons

post-flare loops : bremmsstrahlungand gyrosynchrotron emission from

100 keV electrons

prominences (associated withCMEs) emitting bremsstrahlungprominences (associated withCMEs) emitting bremsstrahlung

active regions with strong magneticfields (>1500 G in the corona), emitting

circularly polarised gyrosynchrotron emission

active regions with strong magneticfields (>1500 G in the corona), emitting

circularly polarised gyrosynchrotron emission

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The Sun in m wavelengths (150-300 MHz)The Sun in m wavelengths (150-300 MHz)

EUV (EIT Fe195)

f=164 MHz f=327 MHz

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The Bastille-day event in m wavelengthsThe Bastille-day event in m wavelengths

(Nançay radioheliograph, K.-L. Klein, 2001)

f=164 MHz f=236 MHz f=327 MHz

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A CME in m wavelengthsA CME in m wavelengths

Two successive imagesfrom the LASCO

coronagraph

Movie from the Nançay radioheliograph@ f=164 MHz : synchrotron emission from

relativistic electrons accelerated at the shock

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GyromagneticGyromagneticemissionemission

In regions where the magneticfield is strong, synchrotronemission (1-30 GHz range) can beused to determine iso-B surfaces

Comparison between radioemission (from the VLA) and

optical measurements (T. Bastian)

J. Lee

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The various uses of radio emission in solar physicsThe various uses of radio emission in solar physics

•• The emission at higher frequencies (visible, EUV, ...) is opticallyThe emission at higher frequencies (visible, EUV, ...) is opticallythin in the corona, whereas radio emission is mostly optically thickthin in the corona, whereas radio emission is mostly optically thick�� multifrequency multifrequency radio emission can be used to radio emission can be used to ‘‘peel awaypeel away’’layers of the solar atmospherelayers of the solar atmosphere

•• radio data provide an almost direct access to the temperatureradio data provide an almost direct access to the temperatureand/or the magnetic field. They are the key the understanding ofand/or the magnetic field. They are the key the understanding ofparticle acceleration.particle acceleration.

•• radio emission presently provides the best technique forradio emission presently provides the best technique fordetermining magnetic fields in the coronadetermining magnetic fields in the corona

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A proxy for sunspots : the f10.7 indexA proxy for sunspots : the f10.7 index

•• For historical and practicalFor historical and practicalreasons, the radio emission atreasons, the radio emission at10.7 cm (3 GHz), integrated10.7 cm (3 GHz), integratedover the whole solar surface,over the whole solar surface,is widely used today as anis widely used today as anproxy for the sunspotproxy for the sunspotnumber.number.

f10.7 index

sunspots

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A proxy for sunspots : the f10.7 indexA proxy for sunspots : the f10.7 index

•• Almost all Almost all thermospheric thermospheric and ionospheric models still use the f10.7and ionospheric models still use the f10.7index as a proxy for the electromagnetic energy input from theindex as a proxy for the electromagnetic energy input from theSun.Sun.

•• There have been suggestions to replace it with spectral lines fromThere have been suggestions to replace it with spectral lines fromthe EUV rangethe EUV range

Conclusion : in space weather, an easilyaccessible but empirical quantity is often

preferable to a physically more meaningfulquantity that isn’t readily available

Conclusion : in space weather, an easilyConclusion : in space weather, an easilyaccessible but empirical quantity is oftenaccessible but empirical quantity is often

preferable to a physically more meaningfulpreferable to a physically more meaningfulquantity that isnquantity that isn’’t readily availablet readily available

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Radio burstsRadio bursts

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A taxonomy of solar radio burstsA taxonomy of solar radio bursts

Type I : continuous radio emission, due to plasma turbulence; enhanced

during flares

Type I : continuous radio emission, due to plasma turbulence; enhanced

during flares

Type II : generated by shockwaves in the corona or in

interplanetary space

Type II : generated by shockwaves in the corona or in

interplanetary space

Type III : plasma waves gene-rated by energetic electrons.Often associated with flares

Type III : plasma waves gene-rated by energetic electrons.Often associated with flares

Type IV : broadband gyro-synchrotron emissionassociated with flares

Type IV : broadband gyro-synchrotron emissionassociated with flares

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Example : radio bursts from the coronaExample : radio bursts from the corona

Hiraiso radiospectrograph

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Interplanetary type II and type III burstsInterplanetary type II and type III bursts

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Dynamic spectrum : an exampleDynamic spectrum : an example

coronaltype II / III

interplanetarytype II boom ! escaping continuum

(AKR, ...)

magnetosph. respondsshock hits Earthinterplanetary shockflare/CME

fpe

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Example of type II and type III emissionExample of type II and type III emission

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Another example : the Bastille-day eventAnother example : the Bastille-day event

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How to easily track type II emissionsHow to easily track type II emissions

Type II emissions occur at the plasma frequency or harmonics thereofType II emissions occur at the plasma frequency or harmonics thereof

but the plasma density on average varies asbut the plasma density on average varies as

In interplanetary space, the shock front propagates at constant speedIn interplanetary space, the shock front propagates at constant speed

�� By plotting 1/f vs time, we should observe straight linesBy plotting 1/f vs time, we should observe straight lines

f ∝ k fpe ∝ ne

ne ∝ r−2

r ∝ v(t − t0 )

1f ∝ v(t − t0 )

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Representation of type II emissionsRepresentation of type II emissions

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A problem : interference with man-made emissionsA problem : interference with man-made emissions

The intensity ofartificial emissionsources varies withtime andgeographicallocation

At 1’000’000 kmaltitude, a 100 kWisotropic emitterradiates as much asthe Sun

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How to avoid pollution ?How to avoid pollution ?

•• Move the detector as far awayMove the detector as far awayas possible from the Earth.as possible from the Earth.�� the L1 Lagrange point is okthe L1 Lagrange point is ok

•• Use several detectors to doUse several detectors to dointerferometry and betterinterferometry and betterreject interferencereject interference

•• Digitize the raw signals asDigitize the raw signals asmuch as possible in order tomuch as possible in order todo digital (do digital (≠≠ analogue) post- analogue) post-processingprocessing

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Real life tends to be more complicatedReal life tends to be more complicated

Type II emission is sensitive to local plasma conditions :Type II emission is sensitive to local plasma conditions :➜➜ intensity and presence of harmonics depends on local conditionsintensity and presence of harmonics depends on local conditions➜➜ cannibalismcannibalism between CMEs with different speeds may affect the between CMEs with different speeds may affect the

emissionemission

(Gopalswamy, 2000)

Fast CME2 catches up slow (invisible) CME1

Fast CME2 catches up slow (invisible) CME1

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How relevant are type II bursts for Space Weather ?How relevant are type II bursts for Space Weather ?

☺☺ Good proxy for earthbound fast CMEs : > 80% of type II emissionsGood proxy for earthbound fast CMEs : > 80% of type II emissionsgive geoeffective CMEsgive geoeffective CMEs

☺☺ Method is simple and can be automatedMethod is simple and can be automated

�� Sensitive detectors are neededSensitive detectors are needed

�� type II emissions are not the universal panacea type II emissions are not the universal panacea➜➜ they are weak and can easily be pollutedthey are weak and can easily be polluted➜➜ we canwe can’’t measure them from groundt measure them from ground➜➜ the physics is not well understoodthe physics is not well understood

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**** Intermission ******** Intermission ****

How does one measure radioHow does one measure radioemission ?emission ?

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How does one measure radio emission ?How does one measure radio emission ?

1) Ground spectrographs

� good spectral resolution (>20 MHz) but no spatial resolution

� examples : Tremsdorf (D), Nançay (F), Culgoora (AUS), ...

Bleien (CH)Tremsdorf (D)

FASR (project)

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How does one measure radio emission ?How does one measure radio emission ?

2) Ground interferometers

� good spatial resolution but limited spectral resolution

� spatial resolution requires large arrays

� examples : Nobeyama (J), Nançay (F), VLA (USA), ...

Nançay (F)Nobeyama (J)

LOFAR (project)

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How does one measure radio emission ?How does one measure radio emission ?

3) Space-borne instruments

� usually with electric field antennae (wires)

� good spectral resolution, no spatial resolution

� no ionospheric cutoff

� examples : Ulysses/URAP, Wind/WAVES, ...

WIND / Waves

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TriangulationTriangulation

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Example : radio triangulation by WIND and UlyssesExample : radio triangulation by WIND and Ulysses

The derived trajectoryof the type III radioburst follows anexpected Parker spiralpath.

The results of theradio triangulationcombined with a driftrate analysis give anaverage electronexciter speed of 0.3c.

(after Reiner et al., JGR, 1998)

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How relevant is triangulation for Space Weather ?How relevant is triangulation for Space Weather ?

☺☺ Concept is simple : this will be tried out with Stereo Concept is simple : this will be tried out with Stereo

�� Works so far for type III bursts only = not a good proxy for CMEs Works so far for type III bursts only = not a good proxy for CMEs

�� Needs three satellites for the accurate location of the radio Needs three satellites for the accurate location of the radiosourcessources

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Interplanetary Scintillation (IPS)Interplanetary Scintillation (IPS)

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IPS : how does it work ?IPS : how does it work ?

The wave-front of radioThe wave-front of radiowaves coming fromwaves coming fromcompact sources (quasars)compact sources (quasars)is deformed by densityis deformed by densityfluctuations.fluctuations.

By correlating receiverBy correlating receiversignals, one can estimatesignals, one can estimatethe density fluctuationthe density fluctuationlevel integrated alonglevel integrated alonglines of sightlines of sight

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IPS and heliospheric disturbancesIPS and heliospheric disturbances

•• High density disturbances are characterised by a fluctuation levelHigh density disturbances are characterised by a fluctuation level(I.e. scintillation index) that exceeds the nominal value(I.e. scintillation index) that exceeds the nominal value

Nominal valueLarge

perturbations

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IPS and CMEsIPS and CMEs

View of the density distribution ofthe Bastille day CME as it reachedthe Earth’s orbit (ellipse) on 15July 2000.

The observer is located 3 AU fromthe Sun and 30° above the eclipticplane (Jackson et al., JGR, 1998)

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IPS : an exampleIPS : an example

Five weeks of reconstructed densityperturbations (Jackson, UCSD)

Comparison with ACE in situ densitymeasurements

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How relevant are IPS for Space Weather ?How relevant are IPS for Space Weather ?

☺☺ Good for solar remote sensing Good for solar remote sensing

☺☺ Potentially useful for forecasting the arrival of heliosphericPotentially useful for forecasting the arrival of heliosphericperturbationsperturbations

�� Time resolution (~1 day) and spatial resolution (a dozen radioTime resolution (~1 day) and spatial resolution (a dozen radiosources) are too limited for doing good 3D imaging of thesources) are too limited for doing good 3D imaging of theheliosphereheliosphere

�� Requires a lot of computation (tomography) Requires a lot of computation (tomography)

�� IPS doesnIPS doesn’’t tell us anything about the topology of the magnetict tell us anything about the topology of the magneticfield, which is essential for assessing geoeffectivenessfield, which is essential for assessing geoeffectiveness

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What next ?What next ?

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Existing and planned facilitiesExisting and planned facilities

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The future : how some would like to have it...The future : how some would like to have it...

•• Ground radio interferometryGround radio interferometry (30 MHz - 3 GHz) : (30 MHz - 3 GHz) :➜➜ need good frequency and time resolution (< 1 second)need good frequency and time resolution (< 1 second)➜➜ digitize the emission as much as possible for better flexibilitydigitize the emission as much as possible for better flexibility➜➜ full time coverage requires at least 3 facilities equally distributed infull time coverage requires at least 3 facilities equally distributed in

longitudelongitude➜➜ close international collaboration and intercalibration are crucialclose international collaboration and intercalibration are crucial➜➜ must have free and easy access to datamust have free and easy access to data

•• Space radio interferometrySpace radio interferometry (100 kHz - 100 MHz) (100 kHz - 100 MHz)➜➜ need a fleet of nanosatellites to do radio interferometry from spaceneed a fleet of nanosatellites to do radio interferometry from space➜➜ electromagnetic pollution is strongly reduced at high orbitselectromagnetic pollution is strongly reduced at high orbits➜➜ allows permanent coverage of the Sunallows permanent coverage of the Sun➜➜ but feasibility not yet proven...but feasibility not yet proven...

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Some useful linksSome useful links

• Links to solar radio observatories http://srbl.caltech.edu/links.html

• The WIND/WAVES homepagehttp://lep694.gsfc.nasa.gov/waves/contents.html

• The STEREO/SWAVES homepagehttp://www-lep.gsfc.nasa.gov/swaves/swaves.html

• The FASR homepage http://www.ovsa.njit.edu/fasr/

• The LOFAR homepage http://www.lofar.org

• Community of European Solar Radio Astronomershttp://www.astro.phys.ethz.ch/rapp/cesra/cesra_home_nf.html